Experimental Study On Formation Characteristics Of Coalbed Methane Hydrate At Mesoscopic Scale

Coal-bed methane?CBM?is a new type of clean energy,which can be used as high-quality energy fuel and chemical raw materials.The main component is methane gas,and other components include nitrogen,oxygen,carbon dioxide,hydrogen sulfide and other gases.The effective content of methane gas directly affects the comprehensive utilization of CBM resources,and improving the concentration of methane gas in CBM can expand its application field and create more economic value.If the methane concentration is not up to the standard,the coal-bed methane will be unable to be used and will be directly discharged,which is far better than the greenhouse effect of CO₂ and the associated harmful gas will cause serious damage to the environment.Therefore,increasing the concentration of methane gas can effectively improve the utilization efficiency of coalbed methane resources,which can not only avoid environmental pollution,but also save the precious energy.As a new technology,hydrate has a very attractive prospect in the separation of methane gas from coalbed methane.Methane gas is superior to other components in coalbed methane in the formation of hydrate,therefore it could be enriched in the hydrate and be separated from other components,so as to achieve the purpose of recovery.The technology of hydrate separation is still being innovated,and the optimization goal is to accelerate the hydrate synthesis process and improve the effective gas storage capacity of hydrate.In this paper,the experiment based on this and the ordered mesoporous materials MCM-41,SBA-15,thermodynamics promoters tetrahydrofuran?THF?and surfactant?SDS?was chosen to conduct the coal bed methane hydrate synthesis experiment in order to study the change characteristics of gas hydrate formation rate and storage at mesoscopic scale.And then comprehensive analysising the reinforcement effect of synthesis of hydrate of mesoporous materials.The experimental temperature and pressure were set at 2.0MPa,1.8MPa,279.15K,276.15K,and 274.15K.The experimental results showed that the formation rate of hydrate in mesoscopic scale was improved and the synthesis time was greatly shortened under the combined action of THF and SDS.The higher the pressure and the lower the temperature in the experimental group,the faster the hydrate formation rate and the larger the final gas storage capacity of the hydrate.By comparing the experimental data of hydrate formation in the two mesoporous materials,it was showed that under the same temperature and pressure,the hydrate synthesis rate in the mesoporous material MCM-41 was faster,while the effective gas storage capacity of the hydrate in the SBA-15 was more,and the difference was not large under the higher pressure.Mesoporous materials SBA-15 and MCM-41 had their own advantages in promoting the hydrate synthesis.Specific applications should be selected according to the actual situation.Using the hydrate phase equilibrium equation?Chen-Guo hydrate model?and PT state equation to predict the phase equilibrium conditions of the hydrate formed about methane?CH₄?,nitrogen?N₂?,and coalbed methane with different methane concentrations in pure water.The results showed that the hydrate model and PT equation of state had a good prediction result on the phase equilibrium condition,and the average error of the prediction result on the pure methane hydrate was 1.24%.The calculated data of coal bed methane hydrate phase equilibrium was worthy of reference.According to the existing separation technology process flow and related equipment,a set of process method of hydrate separation and purification of CBM was constructed,and the specific process flow was introduced,in order to provide some reference for the industrialized application of CBM hydrate separation technology.